cutting 2 wire Bunnings strings

Ltmup

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looking to get a board to use up old lights and wondering if anyone has experience in cutting up 2 wire strings to make large "icicle" type strings to cover roof. yes PSU and special board required
 

Ltmup

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talking with AHH about his new version he is working on
 

i13

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Most of the 2-wire strings are wired like this https://auschristmaslighting.com/attachments/16216/
You can tell that they are wired this way when most of the LEDs have four wires attached to them. When they are wired this way, cutting them up will result in them requiring a lower voltage. The controller might not support such a low voltage. Keep an eye out for tiny resistors hidden below the LEDs; these will change the required voltage for that section.

When using traditional LED strings, you'll need to adjust the voltage and/or resistor(s) so that you get the correct current flowing through each LED. The example in the attachment is a string of 60 LEDs divided into 10 sections. Each section has 3 LEDs wired in reverse; only 3 LEDs in each section can be turned on at a time. If you want to have 10 mA flowing through the LEDs, that would mean that the string should draw a current of 30 mA. If you divide it up, each section should still draw 30 mA in each polarity but the required voltage will be lower.
 

Ltmup

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thanks, kinda thought cutting them up would not be viable. plan B it is
 

Mark_M

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Most of the 2-wire strings are wired like this https://auschristmaslighting.com/attachments/16216/
I remember this talk with @David_AVD last year.

All the strings I've got from Bunnings have been wired differently.
Wiring I've had is this:
31v_2_wire_icicles-easy_read.PNG
So hopefully you could split each series string of 10 LEDs into a drop and you could even remove this annoying reverse-polarity switching.

I made this schematic from when someone was talking about standard icicle strings.
31v_2_wire_icicles.PNG

I've seen the same wiring for Bunnings and Woollies (Woolworths) lights. Icicle and straight strings of lights.
 

i13

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I have seen the wiring that Mark_M has just described but it seems to be much less common than the one that I pictured. It is easy to identify which one you have because in the one that I pictured, most of the LEDs have four wires attached to them. In the one that Mark_M pictured, most of the LEDs have two wires attached to them.

In the one that I pictured, when there are more LEDs, the number of LEDs in each section will be increased but there will usually still be approximately 10 sections. In Mark_M's wiring diagram, a string with more LEDs will have more sections.
 

Ltmup

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thanks for all of the input. While it would be an interesting challenge, it seems to be more effort than effective
 

Mark_M

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I have seen the wiring that Mark_M has just described but it seems to be much less common than the one that I pictured. It is easy to identify which one you have because in the one that I pictured, most of the LEDs have four wires attached to them. In the one that Mark_M pictured, most of the LEDs have two wires attached to them.

In the one that I pictured, when there are more LEDs, the number of LEDs in each section will be increased but there will usually still be approximately 10 sections. In Mark_M's wiring diagram, a string with more LEDs will have more sections.
Just taken this string out of an item, sorry it has hot glue marks.
I have accidently pulled a wire, but this gives me an opportunity to untangle and show the wiring.

Here's 10 LEDs in series across 31v running in parallel across almost the whole string.
IMG_20210428_124519867.jpg

This first LED starts with 5 wires. Two for incoming 31v, two for 31v passed on and one for the first series chain.
IMG_20210428_124530223.jpg

Here is an instance where another section starts. 2 wires go into the last LED of the previous series chain, 1 wire comes out. 2 wires pass on to the next chain.
InkedIMG_20210428_124828246_LI.jpg

At the end, the last 10 LEDs in series only have 2 wires
 

Ltmup

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still working on plan B :) thinking of a squared off zig zag, down across up across down. offset with another strand same same
 
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